Widespread research and development of wireless power transmission techniques has been underway since Massachusetts Institute of Technology (MIT) successfully demonstrated wireless power transmission using magnetic resonance in 2007. Wireless power transmission is also garnering attention as a technique that, when combined with wireless communication, enables the realization of a completely wireless system (“Wireless technology developed to transmit power, lights up a 60 W bulb in tests”, Nikkei Electronics, Vol. 966, Dec. 3, 2007). Furthermore, these days, wireless power transmission techniques continue to spread in a variety of applications, such as charging electric automobiles and hybrid automobiles, charging small electronic devices such as smartphones, and so on. For example, Japanese Patent Laid-Open No. 2013-38924 discloses a power transmission management apparatus that transmits power to a vehicle.
With regard to the safe operation of a wireless power transmitting system, it is necessary to take into consideration objects that may be present in a power transmission-capable area, particularly in systems that can transmit power even when a power transmitting apparatus and a power receiving apparatus are distanced from each other, such as magnetic resonance-based systems. In other words, it is necessary to ensure to the greatest extent possible that power will not be transmitted to obstacles that are not power transmission targets, other unauthenticated devices, and so on located within the power transmission-capable area of the power transmitting apparatus. Furthermore, it is necessary to suppress heat and the like emitted due to a drop in efficiency by ensuring that the power transmitting apparatus transmits power only when the power receiving apparatus is present in an appropriate location in a relative positional relationship with the power transmitting apparatus.
Japanese Patent Laid-Open No. 2013-38924 discloses a method in which authentication is carried out between the power transmitting apparatus and the power receiving apparatus before the power transmitting apparatus transmits power, and power transmission is continued after checking the consistency between a power amount supplied by the power transmitting apparatus and a power amount received by a vehicle. However, when using this method, a large amount of power is transmitted and received immediately after the authentication between the power transmitting apparatus and the power receiving apparatus has ended. Accordingly, there is a problem in that the power transmitting apparatus begins transmitting power even in the case where the power transmitting apparatus and the power receiving apparatus are not in an appropriate positional relationship, resulting in a drop in the transmission efficiency.
The present invention enables wireless power transmission based on the positional relationship between a power transmitting apparatus and a power receiving apparatus.